Subversion Repositories mips_16

/***************************************************

 * Module: alu

 * Project: mips_16

 * Author: fzy

 * Description:

 *     alu implementation

 *

 * Revise history:

 *

 ***************************************************/

`timescale 1ns/1ps

`include "mips_16_defs.v"

module alu

(

        input           [15:0]   a,              //src1

        input           [15:0]   b,              //src2

        input           [2:0]    cmd,    //function sel

        output  reg     [15:0]   r               //result        

);

        always @ (*) begin

                case(cmd)

                        `ALU_NC :

                                r = 16'bx;

                        `ALU_ADD:

                                r = a + b;

                        `ALU_SUB:

                                r = a - b;

                        `ALU_AND:

                                r = a & b;

                        `ALU_OR :

                                r = a | b;

                        `ALU_XOR:

                                r = a ^ b;

                        `ALU_SL :

                                r = a << b;

                        `ALU_SR :

                                r = {{16{a[15]}},a} >> b;

                        `ALU_SRU        :

                                r = {16'b0,a} >> b;

                        default :

                                begin

                                        r = 0;

`ifndef CODE_FOR_SYNTHESIS

                                        $display("ERROR: Unknown alu cmd: %b \n", cmd);

                                        //$stop;

`endif

                                end

                endcase

        end

endmodule